Boll weevils don't hibernate during winter in the subtropics but actually remain active, feeding on orange, grapefruit and other plants, according to an Agricultural Research Service (ARS) scientist studying this infamous cotton pest.

For many years, from south Texas to Argentina, the feeding habits and nutritional requirements of the boll weevil (Anthonomus grandis grandis Boheman) have been poorly understood, making it harder to eradicate the pest.

Despite great strides in controlling the boll weevil, it remains one of the most destructive cotton pests in the Western Hemisphere. The weevils, which feed on and lay eggs in cotton buds, can destroy a crop if left unchecked.

For nearly a decade, ARS entomologist Allan Showler at the agency's Integrated Farming and Natural Resources Research Unit in Weslaco, Texas, has been examining boll weevil ecology in sub-tropical environments. The research refines knowledge on the boll weevil that may help enhance the Boll Weevil Eradication Program in the sub-tropics, run by the U.S. Department of Agriculture (USDA) Animal and Plant Health Inspection Service and supported by ARS research.

The program has enabled cotton farmers to reduce their use of pesticides by between 40 and 100 percent, and increase their cotton yields by at least 10 percent since the program’s inception.

In the winter months, it was previously believed the weevils entered a form of hibernation or dormancy called diapause. But Showler has found that boll weevils generally remain active during winter in the sub-tropics, surviving by feeding on the edible portion of orange, grapefruit and prickly pear cactus, and possibly other plants. Orange and grapefruit can sustain adult boll weevils for as long as eight months — more than enough to see them through the mandatory cotton-free winter period.

The research could help scientists develop new, biological and ecological approaches to controlling the boll weevils. Most of the new proposed tactics recommended by Showler and collaborators do not rely on insecticide use, and the one that does ensures insecticides would be applied when they would be most effective.

Read more about this research in the November/December 2008 issue of Agricultural Research magazine, available online at: http://www.ars.usda.gov/is/AR/archive/nov08/weevils1108.htm.